Desiccants have been used in refrigeration systems for drying, and maintaining dry, refrigerant liquids, such as fluorochlorohydrocarbons. Dry fluid in refrigerant systems is essential because humidity causes serious difficulties such as ice formation or hydrolysis or refrigerant fluids to corrosive acids. The conditions of use vary somewhat from one type of refrigerant system to another. For example, in automotive refrigeration systems, the desiccant is subject to a much higher vibration and attrition than that normally found in non-automotive refrigeration systems. To combat attrition problems in automotive refrigeration, it has been proposed to protect the desiccant in several ways. One known method is to encase desiccant beads or granules in wool or polypropylene felt bags. These bags must be heat sealed or end-sewn to reduce desiccant loss, abrasion and/or dust in the cooling liquid. Further attrition problems are encountered by loosened bag fibers due to cooling liquid flow and vibration. In the case of polypropylene, there is a potential attrition problem and loss of drying efficiency due to melting or thermoplasticity of the polypropylene bags in use. Other attempts have been made to sandwich the desiccant material between fiberglass pads and metal screens. Such assemblies are cumbersome and costly, and difficulties are still encountered by attrition and escape of desiccant.
It has also been proposed to employ drying agents together with binding agents. Bonded blocks of desiccant with aluminum phosphate are suggested in U.S. Pat. No. 2,583,812; organic binders such as phenol-formaldehyde, melamine-formaldehyde, polyvinyl acetate, polyethylene, polyvinyl chloride, polystyrene, methyl cellulose, polyvinylbutyral, epoxide resin formed from epichlorohydrin and Bisphenol-A, i.e., 2,2 bis (4 hydroxyphenyl) propane, and polyurethanes are suggested in U.S. Pat. Nos. 3,025,233; 3,091,550; 3,375,933; 3,687,297; Re. 25,400; 3,545,622 and 3,538,020. These desiccant bodies suffer from one or more disadvantages, for example, rigidity which causes cracking and attrition, insufficient water sorption capacity, swelling or solution in the refrigerant, lack of sufficient permeability for the liquid refrigerant and water molecules, chemical instability, lack of heat resistivity, sensitivity to vibration and shock, and heterogeneity of desiccant particles in the binder matrix, among other disadvantages.